#include <stdio.h>

int main()
{
    int money = 20;
    int kong = 0;
    int m = 0;
    kong = money;
    m = money;
    while(kong > 1)
    {
        m += kong / 2;
        kong = kong / 2 + kong % 2;
    }
    printf("%d", m);
    return 0;
}